feat(rules): add support for function declaration as test case

Add support for the following test file structure.

```js
test('my test', myTest)

function myTest() {
  expect(true).toBe(true)
}
```

Methods that are directly referenced will be ananalyzed for the
following rules `expect-expect` `no-if` `no-test-return-statement`,
`no-try-expect`

src/rules/__tests__/expect-expect.test.ts

@@ -17,6 +17,7 @@ ruleTester.run('expect-expect', rule, {
     'it("should pass", () => expect(true).toBeDefined())',
     'test("should pass", () => expect(true).toBeDefined())',
     'it("should pass", () => somePromise().then(() => expect(true).toBeDefined()))',
+    'it("should pass", myTest); function myTest() { expect(true).toBeDefined() }',
     {
       code:
         'test("should pass", () => { expect(true).toBeDefined(); foo(true).toBe(true); })',
@@ -50,6 +51,15 @@ ruleTester.run('expect-expect', rule, {
         },
       ],
     },
+    {
+      code: 'it("should fail", myTest); function myTest() {}',
+      errors: [
+        {
+          messageId: 'noAssertions',
+          type: AST_NODE_TYPES.CallExpression,
+        },
+      ],
+    },
     {
       code: 'test("should fail", () => {});',
       errors: [

src/rules/__tests__/no-if.test.ts

@@ -17,6 +17,9 @@ ruleTester.run('no-if', rule, {
     {
       code: `it('foo', () => {})`,
     },
+    {
+      code: `it('foo', () => {}); function myTest() { if('bar') {} }`,
+    },
     {
       code: `foo('bar', () => {
         if(baz) {}
@@ -272,6 +275,14 @@ ruleTester.run('no-if', rule, {
         },
       ],
     },
+    {
+      code: `it('foo', myTest); function myTest() { if ('bar') {} }`,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
     {
       code: `describe('foo', () => {
         it('bar', () => {

src/rules/__tests__/no-test-return-statement.test.ts

@@ -23,6 +23,12 @@ ruleTester.run('no-test-prefixes', rule, {
       expect(1).toBe(1);
     });
     `,
+    `
+    it("one", myTest);
+    function myTest() {
+      expect(1).toBe(1);
+    }
+    `,
   ],
   invalid: [
     {
@@ -41,5 +47,14 @@ ruleTester.run('no-test-prefixes', rule, {
       `,
       errors: [{ messageId: 'noReturnValue', column: 9, line: 3 }],
     },
+    {
+      code: `
+        it("one", myTest);
+        function myTest () {
+          return expect(1).toBe(1);
+        }
+      `,
+      errors: [{ messageId: 'noReturnValue', column: 11, line: 4 }],
+    },
   ],
 });

src/rules/__tests__/no-try-expect.test.ts

@@ -14,17 +14,21 @@ ruleTester.run('no-try-catch', rule, {
     `it('foo', () => {
         expect('foo').toEqual('foo');
     })`,
+    `it('foo', () => {})
+    function myTest() {
+      try {
+      } catch {
+      }
+    }`,
     `it('foo', () => {
       expect('bar').toEqual('bar');
     });
     try {
-
     } catch {
       expect('foo').toEqual('foo');
     }`,
     `it.skip('foo');
     try {
-
     } catch {
       expect('foo').toEqual('foo');
     }`,
@@ -44,6 +48,22 @@ ruleTester.run('no-try-catch', rule, {
         },
       ],
     },
+    {
+      code: `it('foo', myTest)
+      function myTest() {
+        try {
+
+        } catch (err) {
+          expect(err).toMatch('Error');
+        }
+      }
+      `,
+      errors: [
+        {
+          messageId: 'noTryExpect',
+        },
+      ],
+    },
     {
       code: `it('foo', async () => {
         await wrapper('production', async () => {

src/rules/expect-expect.ts

@@ -7,7 +7,12 @@ import {
   AST_NODE_TYPES,
   TSESTree,
 } from '@typescript-eslint/experimental-utils';
-import { TestCaseName, createRule, getNodeName } from './utils';
+import {
+  TestCaseName,
+  createRule,
+  getFunctionDeclarationTestCallExpressions,
+  getNodeName,
+} from './utils';
 
 export default createRule<
   [Partial<{ assertFunctionNames: readonly string[] }>],
@@ -39,7 +44,31 @@ export default createRule<
   },
   defaultOptions: [{ assertFunctionNames: ['expect'] }],
   create(context, [{ assertFunctionNames = ['expect'] }]) {
-    const unchecked: TSESTree.CallExpression[] = [];
+    const unchecked: Array<
+      TSESTree.CallExpression | TSESTree.FunctionDeclaration
+    > = [];
+
+    function checkCallExpressionUsed(nodes: TSESTree.Node[]) {
+      for (const node of nodes) {
+        const index =
+          node.type === AST_NODE_TYPES.CallExpression
+            ? unchecked.indexOf(node)
+            : -1;
+
+        if (node.type === AST_NODE_TYPES.FunctionDeclaration) {
+          const nodes = getFunctionDeclarationTestCallExpressions(
+            context,
+            node,
+          );
+          checkCallExpressionUsed(nodes);
+        }
+
+        if (index !== -1) {
+          unchecked.splice(index, 1);
+          break;
+        }
+      }
+    }
 
     return {
       CallExpression(node) {
@@ -48,17 +77,7 @@ export default createRule<
           unchecked.push(node);
         } else if (name && assertFunctionNames.includes(name)) {
           // Return early in case of nested `it` statements.
-          for (const ancestor of context.getAncestors()) {
-            const index =
-              ancestor.type === AST_NODE_TYPES.CallExpression
-                ? unchecked.indexOf(ancestor)
-                : -1;
-
-            if (index !== -1) {
-              unchecked.splice(index, 1);
-              break;
-            }
-          }
+          checkCallExpressionUsed(context.getAncestors());
         }
       },
       'Program:exit'() {

src/rules/no-if.ts

@@ -1,4 +1,10 @@
-import { TestCaseName, createRule, getNodeName, isTestCase } from './utils';
+import {
+  TestCaseName,
+  createRule,
+  getNodeName,
+  isFunctionDeclarationTestCase,
+  isTestCase,
+} from './utils';
 import {
   AST_NODE_TYPES,
   TSESTree,
@@ -63,8 +69,8 @@ export default createRule({
       FunctionExpression() {
         stack.push(false);
       },
-      FunctionDeclaration() {
-        stack.push(false);
+      FunctionDeclaration(node) {
+        stack.push(isFunctionDeclarationTestCase(context, node));
       },
       ArrowFunctionExpression(node) {
         stack.push(isTestArrowFunction(node));

src/rules/no-test-return-statement.ts

@@ -1,4 +1,9 @@
-import { createRule, isFunction, isTestCase } from './utils';
+import {
+  createRule,
+  isFunction,
+  isFunctionDeclarationTestCase,
+  isTestCase,
+} from './utils';
 import { TSESTree } from '@typescript-eslint/experimental-utils';
 
 const RETURN_STATEMENT = 'ReturnStatement';
@@ -41,6 +46,16 @@ export default createRule({
         const returnStmt = body.find(t => t.type === RETURN_STATEMENT);
         if (!returnStmt) return;
 
+        context.report({ messageId: 'noReturnValue', node: returnStmt });
+      },
+      FunctionDeclaration(node) {
+        if (!isFunctionDeclarationTestCase(context, node)) return;
+
+        const returnStmt = node.body.body.find(
+          t => t.type === RETURN_STATEMENT,
+        );
+        if (!returnStmt) return;
+
         context.report({ messageId: 'noReturnValue', node: returnStmt });
       },
     };

src/rules/no-try-expect.ts

@@ -1,5 +1,10 @@
 import { TSESTree } from '@typescript-eslint/experimental-utils';
-import { createRule, isExpectCall, isTestCase } from './utils';
+import {
+  createRule,
+  isExpectCall,
+  isFunctionDeclarationTestCase,
+  isTestCase,
+} from './utils';
 
 export default createRule({
   name: __filename,
@@ -39,6 +44,11 @@ export default createRule({
           });
         }
       },
+      FunctionDeclaration(node) {
+        if (isFunctionDeclarationTestCase(context, node)) {
+          isTest = true;
+        }
+      },
       CatchClause() {
         if (isTest) {
           ++catchDepth;
@@ -54,6 +64,11 @@ export default createRule({
           isTest = false;
         }
       },
+      'FunctionDeclaration:exit'(node) {
+        if (isFunctionDeclarationTestCase(context, node)) {
+          isTest = false;
+        }
+      },
     };
   },
 });

src/rules/utils.ts

@@ -631,6 +631,37 @@ export const isHook = (
   );
 };
 
+export const isFunctionDeclarationTestCase = (
+  context: TSESLint.RuleContext<string, any>,
+  node: TSESTree.FunctionDeclaration,
+): boolean => {
+  return getFunctionDeclarationTestCallExpressions(context, node).length > 0;
+};
+
+export const getFunctionDeclarationTestCallExpressions = (
+  context: TSESLint.RuleContext<string, any>,
+  node: TSESTree.FunctionDeclaration,
+): Array<JestFunctionCallExpression<TestCaseName>> => {
+  const variables = context.getDeclaredVariables(node);
+  return variables.reduce<Array<JestFunctionCallExpression<TestCaseName>>>(
+    (acc, { references }) => {
+      const callExpressions = references
+        .map(({ identifier }) => identifier.parent)
+        .filter<TSESTree.CallExpression>(isCallExpression)
+        .filter(isTestCase);
+
+      return [...acc, ...callExpressions];
+    },
+    [],
+  );
+};
+
+const isCallExpression = (
+  node?: TSESTree.Node,
+): node is TSESTree.CallExpression => {
+  return !!node && node.type === AST_NODE_TYPES.CallExpression;
+};
+
 export const isTestCase = (
   node: TSESTree.CallExpression,
 ): node is JestFunctionCallExpression<TestCaseName> => {